Skin oil
The soil that arrives everywhere a person touches, gets darker as it ages, and is the reason a clean-looking surface still feels tacky.
In detail
Sebum from skin and scalp, transferred by contact. It is present on every surface a household touches repeatedly — a sofa armrest, a headrest, a hairbrush, a door handle, a phone, the shoulders of a coat — and it is easy to overlook because it is invisible until it has collected dust. It is an oily soil, so water alone does nothing and a surfactant is the answer: the professional carpet guidance names body and foot oils among the causes of rapid re-soiling, because oil left in a fibre goes on catching dry soil after the visible mark has gone. It also ages badly, oxidising and darkening over months into a mark much harder to remove than the one that was there at the start. Where it lands changes the method more than its chemistry does. On finished leather the trade guidance is CORNSTARCH FIRST — an absorbent to lift the oil before anything wet touches the hide. On a brush it is what makes a rinse insufficient and a mild detergent sufficient. On carpet it is a case for blotting rather than scrubbing. And it is why bare hands are a handling problem on metals: conservation guidance is explicit that skin salts and oils mark and etch metal surfaces.
Hacks and claims involving this
- Soaking a hairbrush to clean it Does not work
Sources for this page
Sources
Consumer Floor and Furnishings Care Information: carpet topics
Institute of Inspection, Cleaning and Restoration Certification (IICRC) · Trade or professional body
Relied on for: That foot lotion and body oils from people or pets are a named cause of rapid re-soiling, and that oily residues should be prevented from transferring to carpet or rugs. (states this directly)
Leather Care and Cleaning Guide
The Leather Institute, 2011 · Trade or professional body
Relied on for: That oil or grease on leather is treated first with cornstarch as an absorbent, rubbed gently until it coagulates with the oil, before any solvent is used. (states this directly)
Museum Handbook Part I, Appendix O: Curatorial Care of Metal Objects
National Park Service, US Department of the Interior, 2002 · Reference work
Relied on for: That metal objects should not be handled with bare hands because salts and oils from skin mark metals, and that a jeweller's cloth may be used to buff away fingerprints. (states this directly)